The overall goal is to perform experiments which will 1) provide insight into factors regulating the synthesis and degradation of alveolar macrophage proteins, 2) study factors modulating the degradation by macrophages of proteins normally present in the alveolar lining layer and 3) examine the role of macrophage lysosomes in the process of protein degradation. We will study the influence of substrates (glucose, amino acids), hormones (insulin, corticosteroids and glucagon), different oxygen tensions and starvation on protein synthesis, the degradation of slow and fast turning-over macrophage proteins, and the degradation of exogenous proteins (the apoprotein of pulmonary surfactant and serum albumin). We anticipate that these experiments will 1) generate information useful to our understanding of macrophage function, 2) provide a basis for comparing protein metabolism in the macrophage to other cell systems, and 3) will provide information on factors regulating the degradation of phagocytosed proteins.